import rethinkdbdash from "rethinkdbdash"
import callback_decorator from "./callback_decorator"
import session from "express-session"

export default class RethinkStore extends session.Store {

	/**
	 *
	 * @param {Object} options Options
	 * @param {Object} [options.connectionOptions] {@link https://www.rethinkdb.com/api/javascript/#connect}
	 * @param {String} [options.table = "session"] Session table
	 * @param {Number} [options.sessionTimeout = 86400000] Session Timeout in milliseconds
	 * @param {Number} [options.flushInterval = 60000] Interval to delete expired sessions from database
	 */
	constructor(options) {
		super()

		options = options || {}
		this.r = rethinkdbdash(options.connectionOptions)
		this.emit("connect")

		this.sessionTimeout = options.sessionTimeout || 86400000 // 1 day
		this.table = options.table || "session"

		setInterval(() => {
			this.flush()
		}, options.flushInterval || 60000)
	}

	/**
	 * Delete expired sessions
	 *
	 * @returns {Promise}
	 */
	async flush() {
		const r = this.r

		try {
			await r.table(this.table).filter(
				r.row("expires").lt(r.now().toEpochTime().mul(1000))
			).delete()
		} catch (error) {
			console.error(error)
		}
	}

	@callback_decorator
	async get(sid) {
		const r = this.r

		const session_data = await r.table(this.table).get(sid)
		// provide a default for the filter `sess("expires")` operation
		.default({expires: 0})
		// use session or default to determine if session is expired
		.do(sess => r.branch(
			// condition for expiry
			sess("expires").lt(r.now().toEpochTime().mul(1000)),
			// if expired -> delete session and "return" false
			r.table(this.table).get(sid).delete().do(() => false),
			// if not expired -> return the session
			sess
		))

		if (session_data && session_data.data) {
			return session_data.data
		} else {
			return null
		}
	}

	@callback_decorator
	async set(sid, sess) {
		const r = this.r

		const sessionToStore = {
			id: sid,
			expires: this._getTTL(sess),
			data: sess,
		}

		await r.table(this.table).insert(sessionToStore, {
			conflict: "replace",
		})
	}

	/**
	 * Compute TTL for given session
	 *
	 * @param {Object }sess
	 * @returns {Number} TTL
	 * @private
	 */
	_getTTL(sess) {
		return Date.now() + (sess.cookie.originalMaxAge || this.sessionTimeout)
	}

	@callback_decorator
	async destroy(sid) {
		const r = this.r

		await r.table(this.table).get(sid).delete()
	}
}